Lawyers for the Boston Marathon bombing suspect asked a judge Thursday to dismiss the indictment against their client or suspend his trial, saying there weren't enough minorities and younger people in the jury pool.

The move by lawyers for Dzhokhar Tsarnaev came just days before opening statements and testimony are set to begin in his federal death penalty trial.

In their written motion, Tsarnaev's lawyers say the selection process has undermined the required random summoning of potential jurors. They also say the process violated Tsarnaev's constitutional right to have a jury that represents a "fair cross section of the community."

The defense said 1,373 people, summoned from a population of about 5 million in eastern Massachusetts, were originally given numbers based on a random pool order list. New numbers were later assigned, based on when the jurors reported to court to complete written questionnaires.

The defense argues that the reordering undermined the randomness of the selection process and pushed certain groups -- including blacks, people under 30 and people who live in Boston -- down on the list and made them less likely to be chosen for the jury. Only about half of the 1,373 people summoned were considered based on their written questionnaires or questioned individually.

"This re-ordering, apparently based on non-random factors such as arrival time, had systemic effects on the order. The re-ordering was not random and had nonneutral effects on cognizable groups," they wrote in their motion.

For example, a statistician hired by the defense found that the reordering of prospective jurors, on average, pushed the number of black jurors back 43 positions in the order of selection and moved potential white jurors up by three positions.

Prospective jurors who live in Boston were pushed back 25 positions, and those under 30 moved back 13 slots, the defense said.

The statistician, comparing the reordered jurors to their original order, found there were no prospective black jurors among the first 94 people in the new order. He said there would have been five potential black jurors if the court had kept the jurors in their original order.

The defense also argued that the process violated the constitutional cross-section requirement by allowing people over 70 to opt out of jury service. Tsarnaev's lawyers said nearly 96 percent of people over 70 who were summoned as potential jurors opted not to serve.

They also argued that the process did not identify enough prospective black jurors. They said although black people make up 6.14 percent of the population eligible for jury service, they make up only 4.25 percent of the list of names drawn for jury selection.

A spokeswoman for prosecutors declined to comment. The judge did not immediately rule on the request.

Tsarnaev, 21, is accused of carrying out twin bombings at the 2013 marathon. The explosions killed three people and injured more than 260.

Opening statements in the trial are scheduled for March 4.

Tsarnaev's lawyers have argued repeatedly that the trial should be moved out of Massachusetts because of the emotional impact the bombings had in the state and because many people have personal connections to the case. They've been turned down three times by Judge George O'Toole Jr. but last week argued before the 1st U.S. Circuit Court of Appeals. The court has not yet issued its ruling.

Jeff Denner, a veteran Boston defense attorney who is not involved in the case, said he doesn't see a contradiction between the defense push to move the trial out of Massachusetts and its complaint that jurors who live in Boston may have been underrepresented.

"Your first choice would be to get it to a place outside the district of Massachusetts. Your second choice, if you can't do that, you still want at least the people you identify as perhaps having more favorable viewpoints from a defense perspective," Denner said.

"I think they've made a determination that those people are more likely to be upscale urban dwellers who are likely to be more educated and more likely to be more receptive to the kind of political arguments to be made against the application of the death penalty in this particular circumstance."